Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$97.72	4.141%	$101.7666	$101.77	$101.75	$101.80
Purchase #2	$75.70	3.220%	$78.1375	$78.14	$78.15	$78.10
Purchase #3	$75.98	13.125%	$85.9524	$85.95	$85.95	$86.00
Purchase #4	$73.76	12.276%	$82.8148	$82.81	$82.80	$82.80
Purchase #5	$225.94	3.166%	$233.0933	$233.09	$233.10	$233.10
Purchase #6	$132.56	13.550%	$150.5219	$150.52	$150.50	$150.50
Purchase #7	$159.90	11.567%	$178.3956	$178.40	$178.40	$178.40
7 purchase totals =	$841.56		$910.6821	$910.68	$910.65	$910.70